Detection of Minimal Residual Disease by IgH gene rearrangement-PCR in Childhood Acute Lymphoblastic Leukemia

Park, Chan Jeoung; Kim, Mi Chong; Moon, Ae Ran; Seo, Eul Ju; Chi, Hyun Sook; Seo, Jong Jin; Kim, Tae Hyung; Moon, Hyung Nam

Abstract

BACKGROUND
The IgH gene rearrangement (IgH GR) involving highly specific CDR3 region can be used as a minimal residual disease marker in ALL. The IgH GR-PCR has the advantages of the high positive rate in ALL and the detection of clonal evolution.
METHODS
In 30 cases of childhood ALL, the DNA was extracted from the bone marrow aspirates at the diagnosis and during the chemotherapy. The 40 cycle polymerase chain reaction was performed with seven each VH family specific primer and common JH primer. The PCR products were electrophoresed on the agarose gel, and those showing specific bands were electrophoresed on 6M urea 6% polyacrylamide DNA sequencing gel. We compared and analyzed the IgH GR-PCR results, the morphologic diagnosis of the bone marrow and the clinical course.
RESULTS
IgH GR was detected in 93.3% (28/30) at the diagnosis and the rest of two cases showed IgH GR during the therapy. IgH GR was detected in all specimens diagnosed as persistence, partial remission and relapse, the 80.0% of hypocellular marrow with persistence of blasts, the 72.7% of hypocellular marrow, and the 59.2% of complete remission. In the complete remission states the patients with IgH GR showed significantly higher relapse rate (26.2%) than those without IgH GR (7.1%) (p=0.019). Number of clones of IgH GR was from one to five. The more number of clones showed the shorter mean survival time (p=0.1172). The usage of VH3 was most frequent (70.0%). IgH GR had been detected average 3.5 months (range 1-12 months) earlier than the morphologic relapse appeared. During the chemotherapy the evolution of IgH GR was observed in the seven cases (23.3%).
CONCLUSIONS
The IgH GR-PCR will help the understanding of biological characteristics of leukemic cells, the interpretation of the bone marrow studies after chemotherapy and the plans of further therapy, and can be used as a prognostic indicator in the morphologic complete remission state.